Organic compound



Patented Feb. 15, 1944 ORGANIC COMPOUND Roger Adams, Urbana, 111.,assignor to E. I. du Pont de Nemours & Company, Wilmington, DeL, acorporation of Delaware No Drawing. Original application July 27, 1940,

Serial No. 348,073. Divided and this application February 20, 1942,Serial N 0. 431,717

6 Claims.

This invention relates to the preparation of organic compounds and moreparticularly to the preparation of o-diaroylbenzenes which areintermediates for the preparation of 1,3-diarylisobenzofuran' compoundsand to a novel process for their preparation. This application is a division of copending application Serial No. 348,073, filed July 27, 1940.

In copending application Serial No. 348,072 there is described thepreparation of new 1,3-diaryl-4,7-dihydroisobenzoiuran compounds and themethod for producing them from butadienes and 1,2-diaroylethylenes. I

1,3-diphenylisobenzofuran has been prepared as disclosed in the priorart by reacting o-dibenzoylbenzene with zinc inacetic acid. The 1,3-diphenylisobenzofuran has also been produced by the Grignard reactionfrom phenylphthalide. See Boyd 8: Ladham, Journal of the ChemicalSociety, London, 1928, page 2089 and Guyot & Catel Compt. rend. 140;page 1348. I

It is an object of the present invention to provide a new and improvedprocess for the preparation of 1,3-diarylisobenzofurans and also theo-diaroylbenzenes from which they may be produced. It is a furtherobject of the invention to produce new 1,3-diarylisobenzofurans whichare of particular value as oil fluorescent colors. A

still further object of the invention-is to provide lubricating oilswhich are colored by diarylis'obenzofuran compounds and which exhibitstrong and desirable fluorescence.

I have found that 1,3-diaryl-4,7-dihydroisobenzofurans as moreparticularly described in "copending application Serial No. 348,072maybe converted to -1,3-diarylisobenzofurans of the formuladiaroylbenzene and then converted by means of zinc to thediarylisobenzofuran two moles of bro mine are introduced into the4,7-dihydrobenzofuran molecule. The latter reaction may be illustratedas follows:

In the bromination of the 1,3-diaryl-4,7-dihydroisobenzofuran with onemolecule of bromine and the dehydrohalogenation of the resultingcompound to the 1,3-diary1isobenzofuran the removal of two moles ofhydrogen bromide is accomplished by the action of organic amines such aspyridine.

While the conversion of the diaroylbenzenes to 1,3-diarylisobenzofuranwith zinc in acetic acid is a known reaction, it has been found that theyields of the isobenzofuran obtained by this process are by no meanssatisfactory. I have found that materially increased yields may beobtained by the use of zinc with alcoholic caustic alkalies.

By this new process for preparing 1,3-diary1is0- benzofurans newhomologues and analogues of this series may be readily produced byemploying 1,3-diaryl-4,7-dihydroisobenzofurans which carry alkyl or arylgroups in the partially hydrogenated benz-ring, as well as those whichcarry aryl groups of higher molecular weight in the 1,3-positions. Ithas been found that the 1,3- diarylisobenzofurans in which the arylgroups contain at least 12 carbon atoms exhibit strong fluorescence ofdesirable shade when added to lubricating oils which-makes these highermolec- 'ular weight derivatives of particular value. The

there are added 4 parts of the l,3-di-(p- Kenyl)-4,7-dihydroisobenzofuran of Example 2 of co pending application SerialNo. 348,072, and the suspension is heated to boiling. 3.1 parts ofbromine (2 moles) in 16 parts of acetic acid are slowly added, whereuponthe furan compound is rapidly dissolved and the color of the brominedisappears. The mass is refluxed for 45 minutes and the hot solutionpoured into 400-500 parts of hot water and allowed to cool slowly forseveral hours. The mass is filtered and the crude yellow productobtained is redissolved in 44 parts of benzene. The benzene solution istreated with an absorbent carbon such as norit, then evaporated toapproximately three-fifths its volume, cooled and the crystallizedproducts separated by filtration. The o-di-(p-xenoyD-benzene so obtainedwhen recrystallized from a benzene-ligroin mixture has a melting pointof 191-192 0., (Cor.) and is in the form of white crystals.

Example 2 To a hot solution of one-part of ortho-dixenoylbenzene (asobtained in Example 1) in 26 parts of benzene there are added one partof potassium hydroxide and 20 parts of 95% ethanol and one part ofwater. The mixture is then refluxed for two hours during which time thecolor of the solution turns to a dark brownish-yellow. One part ofactivated zinc dust is added and the mass is heated to reflux for 10minutes or until the solution has turned yellow. The solution is thenfiltered while hot and 32 parts of acetic acid and 10 parts of water areadded under agitation. The 1,3-di-(p-xenyl)isobenzofuran is precipitatedout in golden brown crystals. When cool it is removed by filtration andwashed with methanol. On recrystallization from a benzene-ligroinmixture'and a second recrystallization from benzene the 1,3-di-(p-xenyl)-isobenzofuran is obtained with a melting point of 247-249" C. Itdissolves in lubricating oil with a strong bright bluishgreenfluorescence.

Example 3 Example 4 Where the13,5,6-tetraphenyl-4=,'7-dihydroisobenzofuran of copending applicationSerial No. 348,072 is employed the 1,2-diphenyl-4,5-dibenzoylbenzene isobtained which on crystallization from benzene has a melting point of195-'196 C. This product may beconverted by the process described inExample 2 to 1,3.5,6-tetraphenylisobenzofuran which on recrystallizationfrom toluene has a melting point of 282-284" 0.

Example 5 1.3-diphenyl5,6d.imethyl 4,7 -dihydroisobenzofuran isconverted in a similar manner to 1,2- dimethyl-4,5-dibenzcyl-benzenehaving a melting point of 143-144" C. (Cor.) when recrystallized frommethanol. This product may be converted by the process of Example 2 to1,3-diphenyl5,6-

dimethylisobenzofuran having a melting point of 187-188 C. (Cor.).

Example 6 Where 1,3-diphenyl-4,7-dihydroisobenzofuran is employed inExample 1 orthodibenzoylbenzene is obtained which on recrystallizationfrom ethanol or petroleum ether has a melting point of -146" C. (Cor.)This product may then be furan gives 1,2-di-p-chlorobenzoylbenzenehavinga melting point of 167-168 C. which in turn may be converted to1,3-di-p-chlorophenylisobenzofuran having a melting point of 199-200 C.

1,3-di-p-tolyl-4,7-dihydroisobenzofuran gives 1,2- di-p-to1uylbenzenehaving a melting point of 191 and this in turn may be converted ,to 1,3-di-p-tolylisobenzofuran having a melting point of 125 .C.

1,3-di-p-ch1orophenyl-5,6dimethyl 4,7 -.dihy- .droisobenzofuran isconverted to 1.2-,di-p-chlorobenzoyl-4,5-dimethylbenzene having amelting point of 168-169 C. which in turn maybe .con- 'verted to1,3-di-p-chlorophenyl-5,6-dimethylis0- benzofuran having a melting pointof 213 C.

1,3-di--p-tolyl-5,6-dimethyl-4,7-dihydroisobenzofuran is converted to,1,2-di-p-'.toluy1-4,5-dimethylbenzene having a melting point of "164 C.which in turn may be converted to 1,3-.dip-tolyl-5,6-dimethylisobenzofuran havinga melting point of 186 C.

Example .7

To a cold solution of :2 parts of 1,3-diphenyl-4,7-dimethyl-4,7-dihydroisobenzofuran in 16 parts of glacial acetic acidthere is added slowly and with cooling a solution .of "1.07parts ('1mol.) of bromine in 10 parts of acetic acid. The bromine is instantlydecolorized and the .bromination product begins to separate. After theproduct is completely precipitated it is filtered, washed with aceticacid and then with water and dried. This 1,3 diphenyl 4,7-dimethyl-5,6-dibromo- 4,5,6)?-tetrahydroisobenzofuran has a melting point of C.and on recrystallization from N-butanol is obtained as yellow crystalshaving a melting point of 168-170 C. with decomposition.

Alternatively the dibromoederivative may be obtained by directdibromination of the 4,5-dibenzoyl-3,6-dimethylcyclohexene-l,2. Thedibromide thus obtained is ring closed according to the proceduredisclosed in copending application Serial No. 348,072, for thepreparation of the nonbromine-containing 4,7-dihydroisobenzofurans.

Example 8 A solution of two parts of the 4,7-dimethyl5,6.-dibromo-tetrahydroisobenzofuran of Example 7 in ten parts of drypyridine is refluxed for 30 minutes. The solution becomes a brightyellow color and after 1.0 to v15 minutes. crystals of pyridinehydrobromide separate from the solution. The solution is poured intowater and the oil whichseparates soon crystallizes. The crude productmelts at about .115-120 C. This 1,3- diphenyl-4,7 dimethyliso'benzofuranis separated -from any unchanged dibromo-compound by dissolving in etherand separating it from the undissolved dibromo-compound. On evaporationof the ether and recrystallization of the product from methanol, it isobtained as bright yellow crystals having a melting point of 129-131 C.

The alternative procedure described in Examples 7 and 8 may also beemployed in the preparation of the further substituted1,3-diarylisobenzofurans.

The 1,3-diarylisobenzofurans are particularly useful as oil fluorescentcolors and exhibit relatively good light fastness when dissolved in oil.

Any of the 1,3-diaryl-4,7-dihydroisobenzofurans disclosed in copendingapplication Ser. No. 348,072 may be converted to the1,3-diarylisobenzofurans. The l,3-diaryl-4,'7-dihydroisobenzofuranswhich carry high molecular weight aryl groups in the 1,3-position mayalso carry alkyl or aryl radicals in the partially hydrogenatedbenzring.

I claim:

1. Diaryl substituted ortho-dibenzoylbenzenes which carry the two arylgroups in one of the sets of positions 3,6 and 4,5 on the benzene radi-5 cal and the p-positions on the benzoyl groups.

